ASCII Table: Complete ASCII Reference Guide

ASCII (American Standard Code for Information Interchange) is the bedrock of digital text. Published in 1963 and finalized as ANSI X3.4 in 1968, this 7-bit encoding standard defines 128 characters that form the foundation of virtually every modern text encoding system. Whether you're a seasoned developer debugging character encoding issues or a student learning computer science fundamentals, this guide provides every ASCII value you'll ever need in one comprehensive reference.

ASCII Control Characters (Decimal 0–31)

The first 32 positions in the ASCII table (0–31) are reserved for control characters — non-printable codes originally designed to control teletype machines and early computer terminals. While most are invisible, they remain critically important in modern computing for text formatting, network protocols, and terminal control.

Dec	Hex	Char	Name	Modern Use
0	00	NUL	Null	String terminator in C
1	01	SOH	Start of Heading	Unused today
2	02	STX	Start of Text	Unused today
3	03	ETX	End of Text	End-of-transmission in serial
4	04	EOT	End of Transmission	Unix EOF marker (Ctrl+D)
5	05	ENQ	Enquiry	Unused today
6	06	ACK	Acknowledge	Serial protocols
7	07	BEL	Bell	Terminal alert sound
8	08	BS	Backspace	Text editing (Ctrl+H)
9	09	HT	Horizontal Tab	Tab formatting, \t escape
10	0A	LF	Line Feed	Unix newline (\n)
11	0B	VT	Vertical Tab	Rare formatting
12	0C	FF	Form Feed	Page break (\f)
13	0D	CR	Carriage Return	Windows newline (\r)
14	0E	SO	Shift Out	Unused today
15	0F	SI	Shift In	Unused today
16	10	DLE	Data Link Escape	Serial protocols
17	11	DC1	Device Control 1	XON flow control (Ctrl+Q)
18	12	DC2	Device Control 2	Unused today
19	13	DC3	Device Control 3	XOFF flow control (Ctrl+S)
20	14	DC4	Device Control 4	Unused today
21	15	NAK	Negative Ack	Serial protocols
22	16	SYN	Synchronous Idle	Unused today
23	17	ETB	End Trans. Block	Unused today
24	18	CAN	Cancel	Cancel operation
25	19	EM	End of Medium	Unused today
26	1A	SUB	Substitute	Windows EOF marker (Ctrl+Z)
27	1B	ESC	Escape	ANSI escape sequences
28	1C	FS	File Separator	Data delimiting
29	1D	GS	Group Separator	Data delimiting
30	1E	RS	Record Separator	Data delimiting
31	1F	US	Unit Separator	Data delimiting
127	7F	DEL	Delete	Backspace character

The most commonly used control characters today are LF (10) for Unix line endings, CR+LF (13+10) for Windows line endings, TAB (9) for indentation, NUL (0) as a C string terminator, and ESC (27) for terminal color codes and control sequences.

ASCII Printable Characters (Decimal 32–126)

Characters 32 through 126 are the printable ASCII characters — the visible symbols you type on a keyboard every day. This range includes the space character, punctuation marks, digits, uppercase and lowercase letters, and common symbols.

Punctuation and Symbols (32–47)

Dec	Hex	Char	Description
32	20	(space)	Space character
33	21	!	Exclamation mark
34	22	"	Double quotation mark
35	23	#	Number sign (hash)
36	24	$	Dollar sign
37	25	%	Percent sign
38	26	&	Ampersand
39	27	'	Apostrophe (single quote)
40	28	(	Left parenthesis
41	29	)	Right parenthesis
42	2A	*	Asterisk
43	2B	+	Plus sign
44	2C	,	Comma
45	2D	-	Hyphen-minus
46	2E	.	Period (full stop)
47	2F	/	Forward slash

Digits (48–57)

Dec	Hex	Char
48	30	0
49	31	1
50	32	2
51	33	3
52	34	4
53	35	5
54	36	6
55	37	7
56	38	8
57	39	9

Note the useful property: ASCII digit values are sequential, so converting a character digit to its numeric value is simply char - '0' (or char - 48).

Uppercase Letters (65–90)

Dec	Hex	Char	Dec	Hex	Char	Dec	Hex	Char
65	41	A	74	4A	J	83	53	S
66	42	B	75	4B	K	84	54	T
67	43	C	76	4C	L	85	55	U
68	44	D	77	4D	M	86	56	V
69	45	E	78	4E	N	87	57	W
70	46	F	79	4F	O	88	58	X
71	47	G	80	50	P	89	59	Y
72	48	H	81	51	Q	90	5A	Z
73	49	I	82	52	R

Key property: the difference between uppercase and lowercase is exactly 32. So 'a' - 'A' = 32. To convert case, XOR with 32 or add/subtract 32.

Lowercase Letters (97–122)

Dec	Hex	Char	Dec	Hex	Char	Dec	Hex	Char
97	61	a	106	6A	j	115	73	s
98	62	b	107	6B	k	116	74	t
99	63	c	108	6C	l	117	75	u
100	64	d	109	6D	m	118	76	v
101	65	e	110	6E	n	119	77	w
102	66	f	111	6F	o	120	78	x
103	67	g	112	70	p	121	79	y
104	68	h	113	71	q	122	7A	z
105	69	i	114	72	r

Extended ASCII (Decimal 128–255)

Standard ASCII only uses 7 bits (0–127). The 8th bit was originally reserved as a parity bit for error checking in serial communication. When 8-bit computing became common, the upper 128 values (128–255) were repurposed to add additional characters.

There is no single "extended ASCII" standard. Several competing encodings emerged:

• ISO-8859-1 (Latin-1): Western European standard, includes accented characters like é (233), ñ (241), ü (252), and the § symbol (167). Used as the default in early web standards.
• Windows-1252 (CP1252): Microsoft's extension of Latin-1, adds smart quotes (147–148), em dash (151), and the Euro sign € (128). This is the most common extended ASCII encoding in practice.
• Code Page 437: The original IBM PC character set, includes box-drawing characters (┌─┐), Greek letters, and mathematical symbols. Still visible in terminal emulators today.

For a complete interactive reference with all extended characters, use RiseTop's ASCII Table Tool.

ASCII in Programming: Practical Examples

Understanding ASCII values unlocks powerful text manipulation techniques:

// Case conversion using ASCII math
function toLower(ch) {
    return ch >= 65 && ch <= 90 ? ch + 32 : ch;
}
function toUpper(ch) {
    return ch >= 97 && ch <= 122 ? ch - 32 : ch;
}
// Check if character is a digit
function isDigit(ch) { return ch >= 48 && ch <= 57; }
// Check if character is alphanumeric
function isAlpha(ch) {
    return (ch >= 65 && ch <= 90) || (ch >= 97 && ch <= 122);
}

These operations are O(1) and avoid the overhead of regular expressions or library function calls, making them valuable in performance-critical code paths like parsers and tokenizers.

Key ASCII Properties Every Developer Should Know

• Backward compatibility: UTF-8's first 128 characters are identical to ASCII. Every valid ASCII file is a valid UTF-8 file.
• Case difference is 32: 'a' - 'A' = 32. Toggle case with XOR: ch ^= 32.
• Digit ordering: Digits 0-9 are at positions 48-57. Convert digit to number: ch - 48 or ch - '0'.
• Letter ranges: A-Z = 65-90, a-z = 97-122. No other characters exist between them.
• Space is 32: The space character (decimal 32, hex 20) is the most common character in most English texts.
• DEL is 127: The only control character above the printable range, originally designed to delete the previous character on paper tape.

Frequently Asked Questions